Abnormal Nocturnal Plasma Level Of Vasopressin And Aldosterone In Obstructive Sleep Apnea Syndrome

Hypertension is common among patients with obstructive sleep apnea syndrome (OSAS). The mechanisms causing blood pressure elevation are not clarified, but there may be an increased activity in the vasoactive hormonal systems due to numerous hypoxic episodes during the night. The purpose of the study was to measure plasma concentrations of vasopressin (AVP), endotheline (Endot), angiotensin II (Ang II), and aldosterone (Aldo) during the night in patients with OSAS and healthy controls. We wanted to test the hypothesis that patients with OSAS have an abnormal plasma level of vasoactive hormones during night. Fourteen patients with an apnea-hypopnea index higher than 10, and 9 healthy control subjects were included in the study. Blood samples were drawn every second hour from 2030h to 0630h for measurement of AVP, Endot, Ang II, Aldo. Oxygen saturation was recorded continuously. Blood pressure and heart rate were measured immediately before blood sampling. Hormones were determined by radioimmunoassay. AVP was significantly increased in patients with OSAS compared with healthy control subjects during the night (OSAS: 0.70 pg/ml (mean), healthy controls: 1.33 pg/ml, p<0.05). Endot did not differ between patients and controls. Aldo increased during the night in patients with OSAS and was elevated at the end of the night, whereas Ang II was the same in the two groups. The observed time with oxygen saturation below 90% were significantly higher in patients with OSAS than in controls (10.6% versus 0,8%, p<0.01). Patients with OSAS had a higher blood pressure, both systolic and diastolic, compared with healthy control subjects (147/89 versus 127/78, p<0.05/p<0.05). It is concluded that patients with obstructive sleep apnea syndrome have an abnormal nocturnal rhythm in plasma concentrations of vasopressin and aldosterone. It is suggested that increased activity in these hormones is involved in the pathogenesis of hypertension in patients with OSAS.